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G'day Jerry, you said: "When it is close to the ground or near other "antennas" the resistance will drop." And that is very true. Oh, and you omitted to point out that the feed point impedence of a 'folded dipole will be 300 ohms. I believe that was the primary reason for 4:1 baluns and 300 ohm ribbon, as opposed to an open wire feedline; ie. market driven with the advent of TV. But certainly matching with a short length of 300 ohm ribbon is both sound and popular. But getting back to your point as quoted above, I wonder if you have ever placed an impedence bridge on the imput terminals of the average TV yagi? I have not, however, I have assumed (rightly, I believe) that the impedence will be very low, maybe tending toward 15-20 Ohms. If this is correct then using a 4:1 balun on a TV antenna would be very lossy. I live in a lowish field strength area for both vhf and uhf TV, yet by omitting the balun and taking the coax direct the the antenna via a weather loop, I have for the past 20 or so years enjoyed perfect noise free reception (with the minor exception of ch 2 occasionally).
Getting back to radio astronomy, it seems to me that rather than embroiling a novice in toooo much technical stuff, an antenna tuner might be a sound investment; depending on the budget of course. A random wire can be tuned for optimum reception on a variety of bands, or a poorly matched dipole or other, and this might suffice until a deeper commitment is considered justified. Andrews don't seem to have anything under $199, but I'm sure that there will be other suppliers with lower priced (lower power) options.
Cheers,
Doug
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